1. Field of the Invention
This invention concerns a method for threading jet nozzles of weaving machines with a correct length of the weft thread end, and also a weaving machine which uses this method.
The invention is intended in the first place for threading the main nozzles of airjet weaving machines with a correct length of the weft thread end. More generally, however, it can be used in all weaving machines in which the weft threads are inserted into the shed via a jet nozzle by means of a fluid, for example, in weaving machines in which the fluid consists of a liquid, such as water.
2. Description of Related Art
As is known, in airjet weaving machines the weft threads are wound off from yarn packages by means of prewinders, while weft thread lengths are taken one by one from these prewinders and inserted into the shed by means of one or more main nozzles. Whenever a break in the supply of a weft thread occurs, or whenever it is necessary to work with another weft thread, rethreading of the corresponding main nozzle can be done either manually or automatically.
When a weft thread is threaded into the main nozzle manually, the weaver presents the leading end of the thread to the intake of the main nozzle, and then by pressing a pushbutton releases one turn of weft thread from the prewinder. The weft thread is then sucked up by the activated main nozzle. When threading is carried out automatically, the weft thread is presented to the main nozzle automatically, and a number of turns are released automatically, until the leading end of the weft thread reaches at least through the main nozzle.
Clearly, the free end of the weft thread which is brought in will in most cases not be situated precisely at the front end of the main nozzle, but will reach out of the main nozzle. As is known, problems result if the thread end reaching out of the main nozzle is not removed, either because the free thread end may be unintentionally woven into the cloth or because the free thread end makes inserting the next weft thread more difficult. Until now, it has been customary for the weaver to cut off the free thread end after rethreading of the main nozzle. However, since the goal is full automation of weaving machines, manual interventions should clearly be capped to a minimum.